1. Field of the Invention
The present invention concerns a catalyst for hydrotreatment of a hydrocarbon petroleum feed, comprising cobalt, molybdenum and phosphorous.
Hydrotreatment of petroleum cuts is gaining importance in refining, both with the increasing necessity for converting ever heavier fractions and with the increasing severity of specifications for the finished products.
This state of affairs arises from the economic importance of maximally upgrading imported crudes with ever-increasing heavy fractions which have both a relative deficit of hydrogen in those heavy fractions or lighter fractions produced from them, and contain a large quantity of heteroatoms such as sulphur and nitrogen.
In general, hydrotreatment is the purification of hydrocarbon petroleum cuts without significant modification of the backbone defined by the carbon atoms. Thus it includes eliminating heteroatoms such as sulphur and nitrogen, eliminating metals, and partial or complete hydrogenation. When this proves to be necessary, the petroleum cut is hydrotreated then freed of the products formed which means that a purified petroleum cut can be recovered.
The "severity" of hydrotreatment is directly linked to the operating conditions. The term "operating conditions" means the nature of the feed, the total pressure in the reaction zone, the partial pressures of the various compounds, the reaction temperature, the hourly space velocity and the hydrogen flow rate. In general, the heavier the feed, the more difficult it is to convert, the more severe are the operating conditions, i.e., the pressures, temperature and hydrogen flow rate are higher and the hourly space velocity is lower.
2. Related Art
The closest known prior art is Sherwood, EP 0 526 988 A2. Sherwood describes the following catalyst:
1.6-6.0% wt GVIII metal oxide (NiO or CoO preferably NiO) PA1 10.0-25.0% wt GVI metal oxide (Mo O.sub.3 preferred) PA1 1.0-6.0% wt P.sub.2 O.sub.5, 1.5-3.0% preferred having PA1 a surface of 160-210 m.sup.2 /g PA1 Total Pore Volume (TPV) of 0.5-0.65 cc/g PA1 diameters 100-130 .ANG.: 70.0-85.0% TPV
&gt;160 .ANG.&lt;7.5% TPV PA2 &gt;250 .ANG.&lt;4.0% TPV
Sherwood has prepared CoMoP catalyst B (Table II of the Sherwood publication) with 3.3% Co., 15.2% MoO.sub.3 and 1.5% P.sub.2 O.sub.5 having a surface of, 182 m.sup.2 /g and an average pore diameter of 120 .ANG. and a TPV of 0.579 cc/g.
The following table summarizes the pore size distribution of Sherwood's catalysts, particularly CoMoP and NiMoP.
TABLE 1 Sherwood's Catalyst pore size distribution of Catalysts A and B. Pore Size (.ANG.) NiMoP (Ex. A) in % TPV CoMoP (Ex. B) in % TPV &lt;100 12.8 11.2 &lt;130 90.1 85.4 &lt;160 94.2 96.2 100-130 78.1 74.2 100-160 81.4 85.0 &gt;120 43.7 50.2 &gt;130 9.2 14.6 &gt;160 5.9 3.8 &gt;250 3.9 2.2